This application claims priority to an application entitled xe2x80x9cDecoder Having Gain Controller in Mobile Communication Systemxe2x80x9d filed in the Korean Industrial Property Office on Dec. 31, 1998 and assigned Serial No. 98-62726, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to a concatenated iterative decoder for a receiver in a mobile communication system, and in particular, to an iterative decoder having a gain controller for controlling the gain of an extrinsic information signal output from a component decoder in a mobile communication system.
2. Description of the Related Art
Some future mobile communication systems, such as IMT-2000 (CDMA 2000) and UMTS (Universal Mobile Telecommunication System), are expected to use a turbo code, which requires an iterative decoder. Satellite communication systems and deep space communication systems use turbo codes, such as concatenated convolutional codes, concatenated block codes, or product convolutional codes.
A typical iterative decoder is constituted out of a plurality of component decoders serially concatenated. Each component decoder is a SISO (Soft-In Soft-Out), SOVA (Soft Output Viterbi Algorithm), or MAP (Maximum A Posteriori Probability) decoder.
A turbo decoder with two component decoders will be described by way of example. The component decoder at the front end is called the first component decoder and the component decoder at the rear end is called the second component decoder.
The first component decoder receives a systematic code signal, a first parity signal, and a first extrinsic information signal for decoding, and outputs a primary decoded signal including a systematic code signal component and a reliability value component (hereinafter, referred to as second extrinsic information) representing the new extrinsic information of a decoded result. The second component decoder receives the primary decoded signal from the first component decoder and a second parity signal among parity signals on a radio channel, for decoding and outputs a secondary decoded signal including the first extrinsic information signal component representing the new extrinsic information of the secondary decoded result. The first extrinsic information signal component is fed back to the input of the first component decoder.
As described above, the conventional turbo decoder decodes a received signal with extrinsic information generated from each component decoder, regardless of channel status.
It is, therefore, an object of the present invention to provide an iterative decoder having a plurality of component decoders and a gain controller for controlling the gains of the extrinsic information signals generated from the component decoders according to the channel status, in a mobile communication system.
It is another object of the present invention to provide an iterative decoder having a plurality of component decoders and a gain controller for controlling the gains of the extrinsic information signals generated from the component decoders with fixed attenuation values according to channel status in order to optimize decoding in a mobile communication system.
In accordance with one aspect of the present invention, an iterative decoder comprises a first component decoder for receiving a first extrinsic information signal, a first parity signal, and a systematic code signal, decoding the systematic code signal out of the received signals, and generating a primary decoded signal including a second extrinsic information component, where the first and second extrinsic information signals are used for reducing noise in the input signals; a second component decoder for receiving the primary decoded signal from the first component decoder and a second parity signal, decoding the decoded signal out of the received signals, and generating a secondary decoded signal including the first extrinsic information signal; and a gain controller connected between the first and second component decoders, for attenuating the second extrinsic information signal of the decoded signal received from the first component decoder.
In accordance with another aspect of the present invention, an iterative decoder comprises a first component decoder for receiving a first extrinsic information signal, a first parity signal, and a systematic code signal, decoding the systematic code signal out of the received signals, and generating a primary decoded signal including a second extrinsic information component, where the first and second extrinsic information signals are used for reducing noise in the input signals; a second component decoder for receiving the primary decoded signal from the first component decoder and a second parity signal, decoding the decoded signal out of the received signals, and generating a secondary decoded signal including the first extrinsic information signal; and a gain controller connected between the first and second component decoders, for attenuating the first extrinsic information signal in the signal received from the second component decoder.
In accordance with further another aspect of the present invention, an iterative decoder comprises a first component decoder for receiving a first extrinsic information signal, a first parity signal, and a systematic code signal, decoding the systematic code signal out of the received signals, and generating a primary decoded signal including a second extrinsic information component, where the first and second extrinsic information signals for reducing noise in the input signals; a second component decoder for receiving the primary decoded signal from the first component decoder and a second parity signal, decoding the decoded signal out of the received signals, and generating a secondary decoded signal including the first extrinsic information signal; a first gain controller connected between the first and second component decoders, for attenuating the second extrinsic information signal in the primary signal received from the first component decoder; and a second gain controller connected between the first and second component decoders, for attenuating the first extrinsic information signal in the secondary signal received from the second component decoder.